title: "Umpolung" photoinduced charge separation in an anion-bound supramolecular complex.
abstract: A new supramolecular system, consisting of an expanded porphyrin, cyclo[8]pyrrole (C8) and a pyrene carboxylate (Py) is capable not only of electron transfer upon photoexcitation, but results in "umpolung" or a reversal of the predicted charge-separation behavior in that the higher energy radical ion pair, C8.+-Py.- (2.58 eV) is formed as opposed to C8.--Py.+ (1.31 eV). This observation is rationalized in terms of the latter radical ion pair, C8.--Py.+ being in the Marcus inverted region. Transient absorption spectral studies reveal a charge-separated lifetime of 300 micros, which decays to the triplet state of cyclo[8]pyrrole, also an exceedingly long-lived species. The novel features of this noncovalent dyad highlight the potential utility of anion binding in the construction of supramolecular electron transfer systems.
authors.affiliation: Department of Chemistry & Biochemistry, University Station-A5300, The University of Texas, Austin, Texas 78712-0165, USA. sessler@mail.utexas.edu
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Karnas
authors.forename: Sung Kuk
authors.initials: SK
authors.lastname: Kim
authors.forename: Zhongping
authors.initials: Z
authors.lastname: Ou
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Karl M
authors.initials: KM
authors.lastname: Kadish
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D000838:Anions / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry*; D010777:Photochemistry; D013053:Spectrophotometry
chemical_list: D000838:Anions; D009930:Organic Chemicals